Low-frequency noise considerations for sensors based on manganites

International audienceLow frequency noise considerations for sensors based on La0.33Sr0.67MnO3 (LSMO) thin films are discussed in this paper. Thanks to special attention on the film quality, onthe electrical readout electronics and on the patterned geometries, epitaxially grown LSMO thin films can show a very low level of low-frequency noise and can thus be used to fabricate high signal-to-noise ratio sensors such as uncooled bolometers and uncooled low-field magnetoresistances

Sub-nT resolution of single layer sensor based on the AMR effect in La_2/_3Sr_1/_3MnO_3 Thin Films

Single-layer magnetoresistive sensors were designed in a Wheatstone bridge configuration using La_2/_3Sr_1/_3MnO_3 ferromagnetic oxide thin film. Uniaxial anisotropy was induced by performing epitaxial deposition of the films on top of vicinal SrTiO_3 substrate. X-ray scan confirms the high crystalline quality of the films and the magnetic anisotropy was checked by magneto-optical Kerr effect measurements. Thanks to the anisotropic magnetoresistive effect and the very low noise measured in the devices, sub-nT resolution was achieved above 100 Hz at 310 K

Realisation et caracterisation de SQUIDs continus a microponts sur films minces de niobium et dans des constrictions de ceramiquesupraconductrice a haute temperature critique

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Investigation of the near-carrier noise for strain-driven ME laminates by using cross-correlation techniques

International audienceThe near-carrier noise around the longitudinal mechanical resonance of a magnetoelectric laminated composite has been investigated. By simultaneously applying a high-frequency electric field across the piezoelectric phase, the sensor response to low-frequency magnetic signals can be shifted around the "carrier" frequency as side band modulation signals. This magnetoelectric response can appear either as an electric charge via piezoelectric-to-piezoelectric (PP) modulation effects or as a magnetic signal via piezoelectric-to-magnetic (PM) modulation effects. These two signals are detected either with a charge preamplifier or with a coil surrounding the sample and the low-frequency sensor response to the applied magnetic field can be recovered by using two independent synchronous detectors. We have designed an experimental setup to observe the direct (passive) low-frequency noise and the noise corresponding to the two above modulations. Noise cross-correlating measurements were also carried out to investigate the origin of the near-carrier noise. No noise coherence was found between the direct low-frequency noise and the noise resulting from either the PP or the PM modulations. However, a noise coherence factor of more than 50% has been found between the signals recovered from the two modulation techniques. A simple model has been used to explain this effect. The magnetoelectric sensor is considered as a nonlinear forced vibration system. Noise sources passing through such a system can be amplified and distributed around the carriers as side band noise where it hampers the equivalent magnetic noise performance. Electronic-thermal noise caused by dielectric dissipations in the piezoelectric phase can be considered as a noise source with a negligible contribution to the total noise floor. Mechanical-thermal low-frequency excess noise is found to be the only intrinsic noise source which is filtered by the nonlinear ME system and is present as an output n- ar-carrier noise which dominates the noise level after the demodulation processe

Magnetic Sensors Based on AMR Effect in LSMO Thin Films

In this paper, the potentialities of the manganese oxide compound La0.7Sr0.3MnO3 (LSMO) for the realization of sensitive room temperature magnetoresistive sensors are discussed. LSMO films deposited on various types of substrates having different magnetic anisotropies were patterned to form rectangular stripes of width 100 µm and length 300 µm. It is shown that, apart from the well-known colossal magnetoresistance contribution, the anisotropic magnetoresistance effects can be used to exhibit competitive performance at room temperature benefiting from the very low noise of LSMO thin films

Anisotropic magnetoresistance in LSMO thin films

International audienc

Investigations on the equivalent magnetic noise of Magneto(Elasto)Electric sensors by using modulation techniques

International audienceThe equivalent magnetic noise of the magnetoelectric (ME) layered composite sensors has been investigated for various modulation techniques. The ME thin film response to an electric modulation or a magnetic modulation can be sensed by using either a charge amplifier or a coil wound around the sample and then demodulated by a synchronous detector. The equivalent magnetic noise for these excitations methods has been compared. As expected, the low-frequency fluctuations can be lowered when the magnetoelectric sensor is operated in a modulation mode. Results show that these methods can give the same level of equivalent magnetic noise for a certain strain-excitation. In theory, mechanical noise appears as the only dominant noise source after the demodulation process in the case of a certain strong amplitude excitation carrier signal. By using these modulation techniques, an equivalent magnetic noise level of 10-100 pT/Hz at 1 Hz was achieved with DC capability

Theoretical Intrinsic Equivalent Magnetic Noise Evaluation for Magneto (Elasto) Electric Sensors Using Modulation Techniques

International audienceThe equivalent magnetic noise of magnetostrictive-piezoelectric composite sensors, in the passive mode or when magnetic modulation techniques are used, has been investigated theoretically and compared with measurements. Several main noise sources and their contributions to the equivalent magnetic noise spectral density have been analyzed using the fluctuation-dissipation theorem and modeled via Nyquist's noise-expression in the linear and non-linear regime. These theoretical analyzes show that the mechanical loss, related to the interfriction of composites, appears as the dominant noise source for such magnetoelectric modulation techniques

Investigations on the equivalent magnetic noise of Magneto(Elasto)Electric sensors by using modulation techniques", Key Engineering Materials

International audienceThe equivalent magnetic noise of the magnetoelectric (ME) layered composite sensors has been investigated for various modulation techniques. The ME thin film response to an electric modulation or a magnetic modulation can be sensed by using either a charge amplifier or a coil wound around the sample and then demodulated by a synchronous detector. The equivalent magnetic noise for these excitations methods has been compared. As expected, the low-frequency fluctuations can be lowered when the magnetoelectric sensor is operated in a modulation mode. Results show that these methods can give the same level of equivalent magnetic noise for a certain strain-excitation. In theory, mechanical noise appears as the only dominant noise source after the demodulation process in the case of a certain strong amplitude excitation carrier signal. By using these modulation techniques, an equivalent magnetic noise level of 10-100 pT/Hz at 1 Hz was achieved with DC capability